Портал:Геофизика

Темы портала: Деятельность; Культура; География; Здоровье; История; Математика; Природа; Люди; Философия; Религия; Общество; Технологии; Случайный портал

Геофизический портал

Возраст океанической литосферы

Геофизика ( / ˌ dʒ iː oʊ ˈ f ɪ z ɪ k s / ) — это предмет естественной науки, занимающийся физическими процессами и физическими свойствами Землии окружающей ее космической среды, а также использованием количественных методов для их анализа. Геофизики, которые обычно изучают геофизику, физику или одну из наук о Земле на уровне аспирантуры, выполняют исследования по широкому кругу научных дисциплин. Термин геофизика классически относится к приложениям, связанным с твердой землей: форма Земли; ее гравитационные , магнитные поля и электромагнитные поля ; ее внутренняя структура и состав ; ее динамика и их поверхностное выражение в тектонике плит , генерация магм , вулканизм и формирование горных пород. Однако современные геофизические организации и чистые ученые используют более широкое определение, которое включает круговорот воды , включая снег и лед; гидродинамику океанов и атмосферы ; электричество и магнетизм в ионосфере и магнитосфере и солнечно-земную физику ; и аналогичные проблемы, связанные с Луной и другими планетами.

Хотя геофизика была признана отдельной дисциплиной только в 19 веке, ее истоки восходят к древности. Первые магнитные компасы были сделаны из магнитных железняков , в то время как более современные магнитные компасы сыграли важную роль в истории навигации. Первый сейсмический инструмент был построен в 132 году нашей эры. Исаак Ньютон применил свою теорию механики к приливам и прецессии равноденствия ; и были разработаны инструменты для измерения формы Земли, плотности и гравитационного поля, а также компонентов круговорота воды. В 20 веке были разработаны геофизические методы для дистанционного исследования твердой Земли и океана, и геофизика сыграла существенную роль в развитии теории тектоники плит. ( Полная статья... )

Обновить с новыми вариантами ниже (очистить)

Избранные общие статьи

Изображение 1
Автоматический георадар (upGPR) вблизи Swiss Camp ( Гренландия )

Приповерхностная геофизика — это использование геофизических методов для исследования мелкомасштабных объектов в неглубоких (десятки метров) недрах. Она тесно связана с прикладной геофизикой или разведочной геофизикой . Используемые методы включают сейсмическую рефракцию и отражение , гравитацию , магнитные, электрические и электромагнитные методы. Многие из этих методов были разработаны для разведки нефти и, но в настоящее время используются для самых разных приложений, включая археологию , науку об окружающей среде , криминалистику , военную разведку , геотехнические исследования , поиск сокровищ и гидрогеологию . Помимо практических приложений, приповерхностная геофизика включает изучение биогеохимических циклов . ( Полная статья... )
Изображение 2
В геодезии фигура Земли — это размер и форма, используемые для моделирования планеты Земля . Вид фигуры зависит от области применения, включая точность, необходимую для модели. Сферическая Земля — это хорошо известное историческое приближение, которое подходит для географии , астрономии и многих других целей. Было разработано несколько моделей с большей точностью (включая эллипсоид ), чтобы системы координат могли служить точным потребностям навигации , геодезии , кадастра , землепользования и различных других задач. ( Полная статья... )
Image 3
Illustration of the dynamo mechanism that generates the Earth's magnetic field: convection currents of fluid metal in the Earth's outer core, driven by heat flow from the inner core, organized into rolls by the Coriolis force, generate circulating electric currents, which supports the magnetic field.

In physics, the dynamo theory proposes a mechanism by which a celestial body such as Earth or a star generates a magnetic field. The dynamo theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time scales. A dynamo is thought to be the source of the Earth's magnetic field and the magnetic fields of Mercury and the Jovian planets. (Full article...)
Image 4
Magnetic stripes are the result of reversals of the Earth's field and seafloor spreading. New oceanic crust is magnetized as it forms and then it moves away from the ridge in both directions. The models show a ridge (a) about 5 million years ago (b) about 2 million years ago and (c) in the present.

Paleomagnetism (occasionally palaeomagnetism) is the study of prehistoric Earth's magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called paleomagnetists.

Certain magnetic minerals in rocks can record the direction and intensity of Earth's magnetic field at the time they formed. This record provides information on the past behavior of the geomagnetic field and the past location of tectonic plates. The record of geomagnetic reversals preserved in volcanic and sedimentary rock sequences (magnetostratigraphy) provides a time-scale that is used as a geochronologic tool. (Full article...)
Image 5
Earth's gravity measured by NASA GRACE mission, showing deviations from the theoretical gravity of an idealized, smooth Earth, the so-called Earth ellipsoid. Red shows the areas where gravity is stronger than the smooth, standard value, and blue reveals areas where gravity is weaker (Animated version).

The gravity of Earth, denoted by $g$ , is the net acceleration that is imparted to objects due to the combined effect of gravitation (from mass distribution within Earth) and the centrifugal force (from the Earth's rotation).
It is a vector quantity, whose direction coincides with a plumb bob and strength or magnitude is given by the norm $g=\|{\mathit {\mathbf {g} }}\|$ .

In SI units, this acceleration is expressed in metres per second squared (in symbols, m/s² or m·s⁻²) or equivalently in newtons per kilogram (N/kg or N·kg⁻¹). Near Earth's surface, the acceleration due to gravity, accurate to 2 significant figures, is 9.8 m/s² (32 ft/s²). This means that, ignoring the effects of air resistance, the speed of an object falling freely will increase by about 9.8 metres per second (32 ft/s) every second. This quantity is sometimes referred to informally as little $g$ (in contrast, the gravitational constant $G$ is referred to as big $G$ ). (Full article...)
Image 6
Cloud-to-ground lightning. Typically, lightning discharges 30,000 amperes, at up to 100 million volts, and emits light, radio waves, x-rays and even gamma rays. Plasma temperatures in lightning can approach 28,000 kelvins.

Atmospheric electricity describes the electrical charges in the Earth's atmosphere (or that of another planet). The movement of charge between the Earth's surface, the atmosphere, and the ionosphere is known as the global atmospheric electrical circuit. Atmospheric electricity is an interdisciplinary topic with a long history, involving concepts from electrostatics, atmospheric physics, meteorology and Earth science.

Thunderstorms act as a giant battery in the atmosphere, charging up the electrosphere to about 400,000 volts with respect to the surface. This sets up an electric field throughout the atmosphere, which decreases with increase in altitude. Atmospheric ions created by cosmic rays and natural radioactivity move in the electric field, so a very small current flows through the atmosphere, even away from thunderstorms. Near the surface of the Earth, the magnitude of the field is on average around 100 V/m, oriented such that it drives positive charges down. (Full article...)
Image 7
Mineral physics is the science of materials that compose the interior of planets, particularly the Earth. It overlaps with petrophysics, which focuses on whole-rock properties. It provides information that allows interpretation of surface measurements of seismic waves, gravity anomalies, geomagnetic fields and electromagnetic fields in terms of properties in the deep interior of the Earth. This information can be used to provide insights into plate tectonics, mantle convection, the geodynamo and related phenomena.

Laboratory work in mineral physics require high pressure measurements. The most common tool is a diamond anvil cell, which uses diamonds to put a small sample under pressure that can approach the conditions in the Earth's interior. (Full article...)
Image 8
p-wave and s-wave from seismograph

A seismic wave is a mechanical wave of acoustic energy that travels through the Earth or another planetary body. It can result from an earthquake (or generally, a quake), volcanic eruption, magma movement, a large landslide and a large man-made explosion that produces low-frequency acoustic energy. Seismic waves are studied by seismologists, who record the waves using seismometers, hydrophones (in water), or accelerometers. Seismic waves are distinguished from seismic noise (ambient vibration), which is persistent low-amplitude vibration arising from a variety of natural and anthropogenic sources.

The propagation velocity of a seismic wave depends on density and elasticity of the medium as well as the type of wave. Velocity tends to increase with depth through Earth's crust and mantle, but drops sharply going from the mantle to Earth's outer core. (Full article...)
Image 9
This marker indicating sea level is situated between Jerusalem and the Dead Sea.

Mean sea level (MSL, often shortened to sea level) is an average surface level of one or more among Earth's coastal bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead a long-term average of tide gauge readings at a particular reference location.

Sea levels can be affected by many factors and are known to have varied greatly over geological time scales. Current sea level rise is mainly caused by human-induced climate change. When temperatures rise, mountain glaciers and polar ice sheets melt, increasing the amount of water in the oceans, while the existing seawater also expands with heat. Because most of human settlement and infrastructure was built in response to a more-normalized sea level with limited expected change, populations affected by sea level rise will need to invest in climate adaptation to mitigate the worst effects or, when populations are at extreme risk, a process of managed retreat. (Full article...)
Image 10
Artist's depiction of solar wind particles interacting with Earth's magnetosphere. Sizes are not to scale.

A geomagnetic storm, also known as a magnetic storm, is a temporary disturbance of the Earth's magnetosphere caused by a solar wind shock wave.

The disturbance that drives the magnetic storm may be a solar coronal mass ejection (CME) or (much less severely) a co-rotating interaction region (CIR), a high-speed stream of solar wind originating from a coronal hole. The frequency of geomagnetic storms increases and decreases with the sunspot cycle. During solar maxima, geomagnetic storms occur more often, with the majority driven by CMEs. (Full article...)
Image 11
Temperature profile of inner Earth, schematic view (estimated). The red dashed line shows the minimum temperature for the respective mantle rock to melt. The geothermal gradient remains below the melting temperature of the rock, except in the asthenosphere. Sharp rises occur in the uppermost mantle and at the core–mantle boundary.

Geothermal gradient is the rate of change in temperature with respect to increasing depth in Earth's interior. As a general rule, the crust temperature rises with depth due to the heat flow from the much hotter mantle; away from tectonic plate boundaries, temperature rises in about 25–30 °C/km (72–87 °F/mi) of depth near the surface in the continental crust. However, in some cases the temperature may drop with increasing depth, especially near the surface, a phenomenon known as inverse or negative geothermal gradient. The effects of weather, the Sun, and season only reach a depth of roughly 10–20 m (33–66 ft).

Strictly speaking, geo-thermal necessarily refers to Earth, but the concept may be applied to other planets. In SI units, the geothermal gradient is expressed as °C/km, K/km, or mK/m. These are all equivalent. (Full article...)
Image 12
Schiehallion's isolated position and symmetrical shape were well-suited to the experiment

The Schiehallion experiment was an 18th-century experiment to determine the mean density of the Earth. Funded by a grant from the Royal Society, it was conducted in the summer of 1774 around the Scottish mountain of Schiehallion, Perthshire. The experiment involved measuring the tiny deflection of the vertical due to the gravitational attraction of a nearby mountain. Schiehallion was considered the ideal location after a search for candidate mountains, thanks to its isolation and almost symmetrical shape.
The experiment had previously been considered, but rejected, by Isaac Newton as a practical demonstration of his theory of gravitation; however, a team of scientists, notably Nevil Maskelyne, the Astronomer Royal, was convinced that the effect would be detectable and undertook to conduct the experiment. The deflection angle depended on the relative densities and volumes of the Earth and the mountain: if the density and volume of Schiehallion could be ascertained, then so could the density of the Earth. Once this was known, it would in turn yield approximate values for those of the other planets, their moons, and the Sun, previously known only in terms of their relative ratios. (Full article...)
Image 13
In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynamo.

In the space environment close to a planetary body with a dipole magnetic field such as Earth, the field lines resemble a simple magnetic dipole. Farther out, field lines can be significantly distorted by the flow of electrically conducting plasma, as emitted from the Sun (i.e., the solar wind) or a nearby star. Planets having active magnetospheres, like the Earth, are capable of mitigating or blocking the effects of solar radiation or cosmic radiation; in Earth's case, this protects living organisms from harm. Interactions of particles and atmospheres with magnetospheres are studied under the specialized scientific subjects of plasma physics, space physics, and aeronomy. (Full article...)
Image 14
Figure 1: Tidal interaction between the spiral galaxy NGC 169 and a smaller companion

The tidal force or tide-generating force is a gravitational effect that stretches a body along the line towards and away from the center of mass of another body due to spatial variations in strength in gravitational field from the other body. It is responsible for the tides and related phenomena, including solid-earth tides, tidal locking, breaking apart of celestial bodies and formation of ring systems within the Roche limit, and in extreme cases, spaghettification of objects. It arises because the gravitational field exerted on one body by another is not constant across its parts: the nearer side is attracted more strongly than the farther side. The difference is positive in the near side and negative in the far side, which causes a body to get stretched. Thus, the tidal force is also known as the differential force, residual force, or secondary effect of the gravitational field.

In celestial mechanics, the expression tidal force can refer to a situation in which a body or material (for example, tidal water) is mainly under the gravitational influence of a second body (for example, the Earth), but is also perturbed by the gravitational effects of a third body (for example, the Moon). The perturbing force is sometimes in such cases called a tidal force (for example, the perturbing force on the Moon): it is the difference between the force exerted by the third body on the second and the force exerted by the third body on the first. (Full article...)
Image 15
Simplified schematic of only the lunar portion of Earth's tides, showing (exaggerated) high tides at the sublunar point and its antipode for the hypothetical case of an ocean of constant depth without land, and on the assumption that Earth is not rotating; otherwise there is a lag angle. Solar tides not shown.

Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon (and to a much lesser extent, the Sun) and are also caused by the Earth and Moon orbiting one another.

Tide tables can be used for any given locale to find the predicted times and amplitude (or "tidal range").
The predictions are influenced by many factors including the alignment of the Sun and Moon, the phase and amplitude of the tide (pattern of tides in the deep ocean), the amphidromic systems of the oceans, and the shape of the coastline and near-shore bathymetry (see Timing). They are however only predictions, the actual time and height of the tide is affected by wind and atmospheric pressure. Many shorelines experience semi-diurnal tides—two nearly equal high and low tides each day. Other locations have a diurnal tide—one high and low tide each day. A "mixed tide"—two uneven magnitude tides a day—is a third regular category. (Full article...)
Image 16
Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay. The use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features, including the age of fossilized life forms or the age of Earth itself, and can also be used to date a wide range of natural and man-made materials.

Together with stratigraphic principles, radiometric dating methods are used in geochronology to establish the geologic time scale. Among the best-known techniques are radiocarbon dating, potassium–argon dating and uranium–lead dating. By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change. Radiometric dating is also used to date archaeological materials, including ancient artifacts. (Full article...)
Image 17
Geodynamics is a subfield of geophysics dealing with dynamics of the Earth. It applies physics, chemistry and mathematics to the understanding of how mantle convection leads to plate tectonics and geologic phenomena such as seafloor spreading, mountain building, volcanoes, earthquakes, faulting. It also attempts to probe the internal activity by measuring magnetic fields, gravity, and seismic waves, as well as the mineralogy of rocks and their isotopic composition. Methods of geodynamics are also applied to exploration of other planets. (Full article...)
Image 18
The Hollow Moon and the closely related Spaceship Moon are pseudoscientific hypotheses that propose that Earth's Moon is either wholly hollow or otherwise contains a substantial interior space. No scientific evidence exists to support the idea; seismic observations and other data collected since spacecraft began to orbit or land on the Moon indicate that it has a solid, differentiated interior, with a thin crust, extensive mantle, and a dense core which is significantly smaller (in relative terms) than Earth's.

While Hollow Moon hypotheses usually propose the hollow space as the result of natural processes, the related Spaceship Moon hypothesis holds that the moon is an artifact created by an alien civilization; this belief usually coincides with beliefs in UFOs or ancient astronauts. This idea dates from 1970, when two Soviet authors published a short piece in the popular press speculating that the Moon might be "the creation of alien intelligence"; since then, it has occasionally been endorsed by conspiracy theorists like Jim Marrs and David Icke. (Full article...)
Image 19
Computer simulation of Earth's field in a period of normal polarity between reversals. The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of Earth is centered and vertical. The dense clusters of lines are within Earth's core.

Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magnetic field is generated by electric currents due to the motion of convection currents of a mixture of molten iron and nickel in Earth's outer core: these convection currents are caused by heat escaping from the core, a natural process called a geodynamo.

The magnitude of Earth's magnetic field at its surface ranges from 25 to 65 μT (0.25 to 0.65 G). As an approximation, it is represented by a field of a magnetic dipole currently tilted at an angle of about 11° with respect to Earth's rotational axis, as if there were an enormous bar magnet placed at that angle through the center of Earth. The North geomagnetic pole actually represents the South pole of Earth's magnetic field, and conversely the South geomagnetic pole corresponds to the north pole of Earth's magnetic field (because opposite magnetic poles attract and the north end of a magnet, like a compass needle, points toward Earth's South magnetic field, Ellesmere Island, Nunavut, Canada). (Full article...)
Image 20
The Chandler wobble or Chandler variation of latitude is a small deviation in the Earth's axis of rotation relative to the solid earth, which was discovered by and named after American astronomer Seth Carlo Chandler in 1891. It amounts to change of about 9 metres (30 ft) in the point at which the axis intersects the Earth's surface and has a period of 433 days. This wobble, which is an astronomical nutation, combines with another wobble with a period of six years, so that the total polar motion varies with a period of about 7 years.

The Chandler wobble is an example of the kind of motion that can occur for a freely rotating object that is not a sphere; this is called a free nutation. Somewhat confusingly, the direction of the Earth's rotation axis relative to the stars also varies with different periods, and these motions—caused by the tidal forces of the Moon and Sun—are also called nutations, except for the slowest, which are precessions of the equinoxes. (Full article...)
Image 21
A picture of Earth and the Moon from Mars. The presence of the Moon (which has about 1/81 the mass of Earth), is slowing Earth's rotation and extending the day by a little under 2 milliseconds every 100 years.

Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the Moon) and the primary planet that it orbits (e.g. Earth). The acceleration causes a gradual recession of a satellite in a prograde orbit (satellite moving to a higher orbit, away from the primary body), and a corresponding slowdown of the primary's rotation. The process eventually leads to tidal locking, usually of the smaller body first, and later the larger body (e.g. theoretically with Earth in 50 billion years). The Earth–Moon system is the best-studied case.

The similar process of tidal deceleration occurs for satellites that have an orbital period that is shorter than the primary's rotational period, or that orbit in a retrograde direction. (Full article...)
Image 22
The Anahim hotspot is a hypothesized hotspot in the Central Interior of British Columbia, Canada. It has been proposed as the candidate source for volcanism in the Anahim Volcanic Belt, a 300 kilometres (190 miles) long chain of volcanoes and other magmatic features that have undergone erosion. This chain extends from the community of Bella Bella in the west to near the small city of Quesnel in the east. While most volcanoes are created by geological activity at tectonic plate boundaries, the Anahim hotspot is located hundreds of kilometres away from the nearest plate boundary.

The hotspot was first proposed in the 1970s by three scientists who used John Tuzo Wilson's classic hotspot theory. This theory proposes that a single, fixed mantle plume builds volcanoes that then, cut off from their source by the movement of the North American Plate, become increasingly inactive and eventually erode over millions of years. A more recent theory, published in 2001 by the Geological Society of America, suggests that the Anahim hotspot might be supplied by a mantle plume from the upper mantle rather than a deep-seated plume proposed by Wilson. Tomographic imaging has since identified a low-velocity anomaly, indicative of an upwelling plume, that measures roughly 400 kilometres (250 miles) deep. This measurement, however, could be an underestimate as the anomaly might originate deeper inside Earth. (Full article...)
Image 23

The Compton–Belkovich Thorium Anomaly, viewed from the Lunar Reconnaissance Orbiter in 2009

The Compton–Belkovich Thorium Anomaly is a volcanic complex on the far side of the Moon. It was found by a gamma-ray spectrometer in 1998 and is an area of concentrated thorium, a 'fertile' element. Lunar rock samples from the Apollo missions reveal that most lunar volcanism occurred around 3 to 4 billion years ago, but this feature could have formed as recently as 1 billion years ago due to the unknown history of the Moon's far side. (Full article...)
Image 24
Precessional movement of Earth. Earth rotates (white arrows) once a day around its rotational axis (red); this axis itself rotates slowly (white circle), completing a rotation in approximately 26,000 years

In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In the absence of precession, the astronomical body's orbit would show axial parallelism. In particular, axial precession can refer to the gradual shift in the orientation of Earth's axis of rotation in a cycle of approximately 26,000 years. This is similar to the precession of a spinning top, with the axis tracing out a pair of cones joined at their apices. The term "precession" typically refers only to this largest part of the motion; other changes in the alignment of Earth's axis—nutation and polar motion—are much smaller in magnitude.

Earth's precession was historically called the precession of the equinoxes, because the equinoxes moved westward along the ecliptic relative to the fixed stars, opposite to the yearly motion of the Sun along the ecliptic. Historically,
the discovery of the precession of the equinoxes is usually attributed in the West to the 2nd-century-BC astronomer Hipparchus. With improvements in the ability to calculate the gravitational force between planets during the first half of the nineteenth century, it was recognized that the ecliptic itself moved slightly, which was named planetary precession, as early as 1863, while the dominant component was named lunisolar precession. Their combination was named general precession, instead of precession of the equinoxes. (Full article...)
Image 25
Earthquake epicenters occur mostly along tectonic plate boundaries, especially on the Pacific Ring of Fire.

An earthquake – also called a quake, tremor, or temblor – is the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume.

In its most general sense, the word earthquake is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as mining, fracking, and nuclear tests. The initial point of rupture is called the hypocenter or focus, while the ground level directly above it is the epicenter. Earthquakes are primarily caused by geological faults, but also by volcanic activity, landslides, and other seismic events. The frequency, type, and size of earthquakes in an area define its seismic activity, reflecting the average rate of seismic energy release. (Full article...)

Избранный геофизик

Image 1

Патрик Блэкетт, ок. 1948 г.

Патрик Мейнард Стюарт Блэкетт, барон Блэкетт , OM , CH , FRS (18 ноября 1897 г. – 13 июля 1974 г.) – британский физик- экспериментатор , известный своими работами по камерам Вильсона , космическим лучам и палеомагнетизму , удостоенный Нобелевской премии по физике в 1948 г. В 1925 г. он стал первым человеком, доказавшим, что радиоактивность может вызывать ядерную трансмутацию одного химического элемента в другой. Он также внес большой вклад во Вторую мировую войну, консультируя по вопросам военной стратегии и разрабатывая оперативные исследования . Его взгляды нашли отражение в развитии третьего мира и влиянии на политику лейбористского правительства 1960-х гг. ( Полная статья... )
Image 2

Birch, c. 1970

Albert Francis Birch (August 22, 1903 – January 30, 1992) was an American geophysicist. He is considered one of the founders of solid Earth geophysics. He is also known for his part in the atomic bombing of Hiroshima and Nagasaki.

During World War II, Birch participated in the Manhattan Project, working on the design and development of the gun-type nuclear weapon known as Little Boy. He oversaw its manufacture, and went to Tinian to supervise its assembly and loading into Enola Gay, the Boeing B-29 Superfortress tasked with dropping the bomb. (Full article...)
Image 3

Portrait by Christian Albrecht Jensen, 1840 (copy from Gottlieb Biermann, 1887)

Johann Carl Friedrich Gauss (German: Gauß [kaʁl ˈfʁiːdʁɪç ˈɡaʊs] ^ⓘ; Latin: Carolus Fridericus Gauss; 30 April 1777 – 23 February 1855) was a German mathematician, astronomer, geodesist, and physicist who contributed to many fields in mathematics and science. He was director of the Göttingen Observatory and professor of astronomy from 1807 until his death in 1855.

While studying at the University of Göttingen, he propounded several mathematical theorems. Gauss completed his masterpieces Disquisitiones Arithmeticae and Theoria motus corporum coelestium as a private scholar. He gave the second and third complete proofs of the fundamental theorem of algebra, made contributions to number theory, and developed the theories of binary and ternary quadratic forms. (Full article...)
Image 4

Van Allen at the National Air and Space Museum, 1977

James Alfred Van Allen (September 7, 1914 – August 9, 2006) was an American space physicist at the University of Iowa. He was instrumental in establishing the field of magnetospheric research in space.

The Van Allen radiation belts were named after him, following his discovery using Geiger–Müller tube instruments on the 1958 satellites (Explorer 1, Explorer 3, and Pioneer 3) during the International Geophysical Year. Van Allen led the scientific community in putting scientific research instruments on space satellites. (Full article...)
Image 5

Wegener, c. 1924–1930

Alfred Lothar Wegener (/ˈveɪɡənər/; German: [ˈʔalfʁeːt ˈveːɡənɐ]; 1 November 1880 – November 1930) was a German climatologist, geologist, geophysicist, meteorologist, and polar researcher.

During his lifetime he was primarily known for his achievements in meteorology and as a pioneer of polar research, but today he is most remembered as the originator of continental drift hypothesis by suggesting in 1912 that the continents are slowly drifting around the Earth (German: Kontinentalverschiebung). (Full article...)
Image 6

John Tuzo Wilson in 1992

John Tuzo Wilson (October 24, 1908 – April 15, 1993) was a Canadian geophysicist and geologist who achieved worldwide acclaim for his contributions to the theory of plate tectonics.

Plate tectonics is the scientific theory that the rigid outer layers of the Earth (crust and part of the upper mantle), the lithosphere, is broken up into around 13 pieces or "plates" that move independently over the weaker asthenosphere. Wilson maintained that the Hawaiian Islands were formed as a tectonic plate (extending across much of the Pacific Ocean) shifted to the northwest over a fixed hotspot, spawning a long series of volcanoes. He also conceived of the transform fault, a major plate boundary where two plates move past each other horizontally (e.g., the San Andreas Fault). (Full article...)
Image 7

Parker in 2018 at the launch of the solar probe that bears his name

Eugene Newman Parker (June 10, 1927 – March 15, 2022) was an American solar and plasma physicist. In the 1950s he proposed the existence of the solar wind and that the magnetic field in the outer Solar System would be in the shape of a Parker spiral, predictions that were later confirmed by spacecraft measurements. In 1987, Parker proposed the existence of nanoflares, a leading candidate to explain the coronal heating problem.

Parker obtained his PhD from Caltech and spent four years as a postdoctoral researcher at the University of Utah. He joined University of Chicago in 1955 and spent the rest of his career there, holding positions in the physics department, the astronomy and astrophysics department, and the Enrico Fermi Institute. Parker was elected to the National Academy of Sciences in 1967. In 2017, NASA named its Parker Solar Probe in his honor, the first NASA spacecraft named after a living person. (Full article...)
Image 8

Henry Cavendish FRS (/ˈkævəndɪʃ/ KAV-ən-dish; 10 October 1731 – 24 February 1810) was an English natural
philosopher and scientist who was an important experimental and theoretical chemist and physicist. He is noted for his discovery of hydrogen, which he termed "inflammable air". He described the density of inflammable air, which formed water on combustion, in a 1766 paper, On Factitious Airs. Antoine Lavoisier later reproduced Cavendish's experiment and gave the element its name.

A shy man, Cavendish was distinguished for great accuracy and precision in his researches into the composition of atmospheric air, the properties of different gases, the synthesis of water, the law governing electrical attraction and repulsion, a mechanical theory of heat, and calculations of the density (and hence the mass) of the Earth. His experiment to measure the density of the Earth (which, in turn, allows the gravitational constant to be calculated) has come to be known as the Cavendish experiment. (Full article...)
Image 9

Portrait by Joseph Karl Stieler (1843)

Friedrich Wilhelm Heinrich Alexander von Humboldt (14 September 1769 – 6 May 1859) was a German polymath, geographer, naturalist, explorer, and proponent of Romantic philosophy and science. He was the younger brother of the Prussian minister, philosopher, and linguist Wilhelm von Humboldt (1767–1835). Humboldt's quantitative work on botanical geography laid the foundation for the field of biogeography, while his advocacy of long-term systematic geophysical measurement pioneered modern geomagnetic and meteorological monitoring. Humboldt and Carl Ritter are both regarded as the founders of modern geography as they established it as an independent scientific discipline.

Between 1799 and 1804, Humboldt travelled extensively in the Americas, exploring and describing them for the first time from a non-Spanish European scientific point of view. His description of the journey was written up and published in several volumes over 21 years. Humboldt was one of the first people to propose that the lands bordering the Atlantic Ocean were once joined (South America and Africa in particular). (Full article...)
Image 10

Portrait by Asta Nørregaard, 1900

Kristian Olaf Bernhard Birkeland (born 13 December 1867 – 15 June 1917) was a Norwegian space physicist, inventor, and professor of physics at the Royal Fredriks University in Oslo. He is best remembered for his theories of atmospheric electric currents that elucidated the nature of the aurora borealis. In order to fund his research on the aurorae, he invented the electromagnetic cannon and the Birkeland–Eyde process of fixing nitrogen from the air. Birkeland was nominated for the Nobel Prize seven times. (Full article...)
Image 11

Bust of Shen at the Beijing Ancient Observatory

Shen Kuo (Chinese: 沈括; 1031–1095) or Shen Gua, courtesy name Cunzhong (存中) and pseudonym Mengqi (now usually given as Mengxi) Weng (夢溪翁), was a Chinese polymath, scientist, and statesman of the Song dynasty (960–1279). Shen was a master in many fields of study including mathematics, optics, and horology. In his career as a civil servant, he became a finance minister, governmental state inspector, head official for the Bureau of Astronomy in the Song court, Assistant Minister of Imperial Hospitality, and also served as an academic chancellor. At court his political allegiance was to the Reformist faction known as the New Policies Group, headed by Chancellor Wang Anshi (1021–1085).

In his Dream Pool Essays or Dream Torrent Essays (夢溪筆談; Mengxi Bitan) of 1088, Shen was the first to describe the magnetic needle compass, which would be used for navigation (first described in Europe by Alexander Neckam in 1187). Shen discovered the concept of true north in terms of magnetic declination towards the north pole, with experimentation of suspended magnetic needles and "the improved meridian determined by Shen's [astronomical] measurement of the distance between the pole star and true north". This was the decisive step in human history to make compasses more useful for navigation, and may have been a concept unknown in Europe for another four hundred years (evidence of German sundials made circa 1450 show markings similar to Chinese geomancers' compasses in regard to declination). (Full article...)
Image 12

Charles Richter, c. 1970

Charles Francis Richter (/ˈrɪktər/; April 26, 1900 – September 30, 1985) was an American seismologist and physicist. He is the namesake and one of the creators of the Richter magnitude scale, which, until the development of the moment magnitude scale in 1979, was widely used to quantify the size of earthquakes. Inspired by Kiyoo Wadati's 1928 paper on shallow and deep earthquakes, Richter first used the scale in 1935 after developing it in collaboration with Beno Gutenberg; both worked at the California Institute of Technology. (Full article...)
Image 13

Broecker c. 2010

Wallace "Wally" Smith Broecker (November 29, 1931 – February 18, 2019) was an American geochemist. He was the Newberry Professor in the Department of Earth and Environmental Sciences at Columbia University, a scientist at Columbia's Lamont–Doherty Earth Observatory and a sustainability fellow at Arizona State University. He developed the idea of a global "conveyor belt" linking the circulation of the global ocean and made major contributions to the science of the carbon cycle and the use of chemical tracers and isotope dating in oceanography. Broecker popularized the term "global warming". He received the Crafoord Prize and the Vetlesen Prize. (Full article...)
Image 14

A stamp of Zhang Heng issued by China Post in 1955

Zhang Heng (Chinese: 張衡; AD 78–139), formerly romanized Chang Heng, was a Chinese polymathic scientist and statesman who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, mathematician, seismologist, hydraulic engineer, inventor, geographer, cartographer, ethnographer, artist, poet, philosopher, politician, and literary scholar.

Zhang Heng began his career as a minor civil servant in Nanyang. Eventually, he became Chief Astronomer, Prefect of the Majors for Official Carriages, and then Palace Attendant at the imperial court. His uncompromising stance on historical and calendrical issues led to his becoming a controversial figure, preventing him from rising to the status of Grand Historian. His political rivalry with the palace eunuchs during the reign of Emperor Shun (r. 125–144) led to his decision to retire from the central court to serve as an administrator of Hejian Kingdom in present-day Hebei. Zhang returned home to Nanyang for a short time, before being recalled to serve in the capital once more in 138. He died there a year later, in 139. (Full article...)
Image 15

Portrait of Andrija Mohorovičić

Andrija Mohorovičić (23 January 1857 – 18 December 1936) was a Croatian geophysicist. He is best known for the eponymous Mohorovičić discontinuity and is considered one of the founders of modern seismology. (Full article...)
Image 16
Richard Doell (1923 – March 6, 2008) was an American geophysicist, known for developing the time scale for geomagnetic reversals with Allan V. Cox and Brent Dalrymple. This work was a major step in the development of plate tectonics. Doell shared the Vetlesen Prize with Cox and Dalrymple. (Full article...)
Image 17

Portrait by Joseph Duplessis, 1778

Benjamin Franklin (January 17, 1706 [O.S. January 6, 1705] – April 17, 1790) was an American polymath: a leading writer, scientist, inventor, statesman, diplomat, printer, publisher and political philosopher. Among the most influential intellectuals of his time, Franklin was one of the Founding Fathers of the United States; a drafter and signer of the Declaration of Independence; and the first postmaster general.

Franklin became a successful newspaper editor and printer in Philadelphia, the leading city in the colonies, publishing the Pennsylvania Gazette at age 23. He became wealthy publishing this and Poor Richard's Almanack, which he wrote under the pseudonym "Richard Saunders". After 1767, he was associated with the Pennsylvania Chronicle, a newspaper known for its revolutionary sentiments and criticisms of the policies of the British Parliament and the Crown. He pioneered and was the first president of the Academy and College of Philadelphia, which opened in 1751 and later became the University of Pennsylvania. He organized and was the first secretary of the American Philosophical Society and was elected its president in 1769. He was appointed deputy postmaster-general for the British colonies in 1753, which enabled him to set up the first national communications network. (Full article...)
Image 18

Adam Marian Dziewoński (November 15, 1936 – March 1, 2016) was a Polish-American geophysicist who made seminal contributions to the determination of the large-scale structure of the Earth's interior and the nature of earthquakes using seismological methods. He spent most of his career at Harvard University, where he was the Frank B. Baird, Jr. Professor of Science. (Full article...)
Image 19

William Gilbert

William Gilbert (/ˈɡɪlbərt/; 24 May 1544? – 30 November 1603), also known as Gilberd, was an English physician, physicist and natural philosopher. He passionately rejected both the prevailing Aristotelian philosophy and the Scholastic method of university teaching. He is remembered today largely for his book De Magnete (1600).

A unit of magnetomotive force, also known as magnetic potential, was named the Gilbert in his honour; it has now been superseded by the Ampere-turn. (Full article...)
Image 20

Richard Dixon Oldham

Richard Dixon Oldham FRS (/ˈoʊldəm/; 31 July 1858 – 15 July 1936) was a British geologist who made the first clear identification of the separate arrivals of P-waves, S-waves and surface waves on seismograms and the first clear evidence that the Earth has a central core. (Full article...)

Избранные изображения

Image 1Анимация цунами , вызванного землетрясением в Индийском океане в 2004 году (из Seismology )
Image 2Земная кора и мантия, разрыв Мохоровичича между нижней частью коры и твердой верхней частью мантии (из Внутреннее строение Земли )
Image 3Изменения виртуального осевого дипольного момента с момента последней инверсии (из магнитного поля Земли )
Image 4Геомагнитная полярность в конце кайнозойской эры . Темные области обозначают периоды, когда полярность совпадает с сегодняшней, светлые области обозначают периоды, когда эта полярность обратная. (из магнитного поля Земли )
Image 5Кристаллы апатита широко используются в датировании по трекам деления. (из Радиометрического датирования )
Image 6Изохроны Lu-Hf , построенные по образцам метеоритов. Возраст рассчитывается по наклону изохроны (линии), а исходный состав — по пересечению изохроны с осью Y. (из Радиометрического датирования )
Image 7Компьютерное моделирование поля Земли в период нормальной полярности между инверсиями. Линии представляют собой линии магнитного поля, синие, когда поле направлено к центру, и желтые, когда от него. Ось вращения Земли центрирована и вертикальна. Плотные скопления линий находятся внутри ядра Земли. (из магнитного поля Земли )
Image 8Установка временной сейсмической станции, северная часть Исландии. (из Seismology )
Image 9Пример квадрупольного поля. Его также можно построить, перемещая два диполя вместе. (из магнитного поля Земли )
Image 10Компьютерное моделирование магнитного поля Земли в период нормальной полярности между инверсиями (из Geophysics )
Image 11Изображение атмосферного электричества в марсианской пылевой буре, которое было предложено в качестве возможного объяснения загадочных химических результатов на Марсе (см. также биологические эксперименты спускаемого аппарата Viking ) (из раздела «Атмосферное электричество »)
Image 12Молния облако-земля . Обычно молния разряжается силой 30 000 ампер , напряжением до 100 миллионов вольт и испускает свет, радиоволны, рентгеновские лучи и даже гамма-лучи . Температура плазмы в молнии может достигать 28 000 кельвинов . (из Атмосферное электричество )
Image 13Геологическое сечение Земли, показывающее различные слои ее недр. (из Внутреннее строение Земли )
Image 14Фотография Земли , сделанная экипажем Аполлона-17 в 1972 году. Обработанная версия стала широко известна как «Голубой шарик» . (из книги «Внутренняя структура Земли »).
Image 15Модель коротковолновых особенностей магнитного поля Земли, приписываемых литосферным аномалиям ( магнитного поля Земли )
Image 16Схема, иллюстрирующая связь между движением проводящей жидкости, организованной в рулоны силой Кориолиса, и магнитным полем, которое генерируется этим движением. (из магнитного поля Земли )
Image 17Последовательность молний (Продолжительность: 0,32 секунды) (из Атмосферного электричества )
Image 18Масс-спектрометр с термической ионизацией, используемый при радиометрическом датировании. (из Радиометрическое датирование )
Image 19Расчетные контуры склонения по годам с 1590 по 1990 (нажмите, чтобы увидеть изменение) (из магнитного поля Земли )
Image 20Фон : набор следов от магнитных обсерваторий, показывающих магнитную бурю в 2000 году. Глобус: карта, показывающая расположение обсерваторий и контурные линии, показывающие горизонтальную магнитную напряженность в мкТл
. ( из магнитного поля Земли )
Image 21Пример радиоактивной цепочки распада от свинца-212 ( ²¹² Pb) до свинца-208 ( ²⁰⁸ Pb). Каждый родительский нуклид спонтанно распадается на дочерний нуклид ( продукт распада ) через α-распад или β ^- распад . Конечный продукт распада, свинец-208 ( ²⁰⁸ Pb), стабилен и больше не может подвергаться спонтанному радиоактивному распаду. (из Радиометрического датирования )
Image 22Сила аксиальной дипольной составляющей магнитного поля Земли с 1600 по 2020 гг. (из магнитного поля Земли )
Image 23Модель тепловой конвекции в мантии Земли . Тонкие красные столбы — мантийные плюмы .
Image 24Схема геодинамо и магнитного поля Земли, которые могли быть вызваны в ранней истории Земли кристаллизацией оксида магния , диоксида кремния и оксида железа (II) (из книги «Внутреннее строение Земли »)
Image 25Движение Северного магнитного полюса Земли через канадскую Арктику (из магнитного поля Земли )
Image 26Схематическое изображение сферических гармоник на сфере и их узловых линий. $P ℓ m$ равна 0 вдоль $m$ больших окружностей, проходящих через полюса, и вдоль $ℓ- m$ окружностей равной широты. Функция меняет знак каждый ℓраз, когда она пересекает одну из этих линий. (из магнитного поля Земли )
Image 27Возраст морского дна. Большая часть информации о датировке поступает из магнитных аномалий.
Image 28Основные плиты Земли :
(из Внутреннее строение Земли )
Image 29Камни Але в Косеберге, примерно в десяти километрах к юго-востоку от Истада , Швеция, были датированы 56 годом н. э. с использованием метода радиоуглеродного анализа органического материала, найденного на месте раскопок. (Из радиометрического датирования )
Image 30Художественное представление структуры магнитосферы. 1) Головная ударная волна. 2) Магнитооболочка. 3) Магнитопауза. 4) Магнитосфера. 5) Северная доля хвоста. 6) Южная доля хвоста. 7) Плазмасфера. (из магнитного поля Земли )
Image 31Общие системы координат, используемые для представления магнитного поля Земли (из Earth's magnetic field )
Image 32Диаграмма конкордии, используемая при датировании урана и свинца , с данными из пояса Пфанзе, Зимбабве . Все образцы показывают потерю изотопов свинца, но пересечение эррохрона (прямая линия через точки образца) и конкордии (кривая) показывает правильный возраст породы. (из радиометрического датирования )
Image 33Карта мира, показывающая частоту ударов молний, в вспышках на км ² в год (равноплощадная проекция). Молнии чаще всего случаются в Демократической Республике Конго . Объединенные данные за 1995–2003 гг. от оптического детектора переходных процессов и данные за 1998–2003 гг. от датчика визуализации молний. (из Атмосферное электричество )
Image 34Связь между полюсами Земли. A1 и A2 — географические полюса; B1 и B2 — геомагнитные полюса; C1 (южный) и C2 (северный) — магнитные полюса. (из магнитного поля Земли )

Подкатегории

Категория головоломка

Выберите [►] для просмотра подкатегорий

Геофизика

Атмосферное электричество

Изменчивость и изменение климата

Разведочная геофизика

Геофизические журналы

Списки геофизики

Геофизические организации

Радиометрическое датирование

Вы знали ...?

... что в рифте Грегори в Восточной Африке находится единственный в мире действующий карбонатитовый вулкан Ол-Доиньо-Ленгаи (на фото) ?
...что одним из способов расчета расстояний по широте и долготе является формула Гаверсина ?
...что суперконтинент Паннотия просуществовал всего около шестидесяти миллионов лет, прежде чем распался на четыре континента ?
... что землетрясение на Суматре 2002 года считается предвестником землетрясения в Индийском океане 2004 года ?

В новостях

5 декабря 2019 г.: Землетрясения в разломе Каскадия могут спровоцировать землетрясения в разломе Сан-Андреас (природа)
10 декабря 2019 г./20 января 2020 г.: Новые данные свидетельствуют о том, что магнитное поле Земли существовало 3,7 миллиарда лет назад (Nature) или, возможно, даже 4,2 миллиарда лет назад (Science)
13 января 2020 г.: Бразилия открывает «впечатляющую» исследовательскую базу в Антарктиде (Наука)